What Is Chiari Malformation Type 1?

Chiari malformation type 1 occurs when a part of the brain — the cerebellum — protrudes through the opening at the base of the skull. While it is most commonly a congenital issue, physicians typically do not detect Chiari malformation type 1 until adolescence or adulthood. Patients can also acquire and develop Chiari malformation type 1 after birth as a result of infection or injury.

Many patients with Chiari malformation type 1 have no symptoms. Others, however, exhibit symptoms due to the development of a syrinx, which is a fluid-filled cavity either in the brain stem (syringobulbia) or spinal cord (known as a syringomyelia). Symptoms vary greatly and may include neck and head pain, dizziness, loss of arm or hand strength, sleep apnea, or double or blurred vision.

For patients without symptoms, doctors usually recommend monitoring as a treatment. For patients with symptoms, surgery may be recommended. Decompression surgery is the most common type of surgery for Chiari malformation type 1. At Neurosurgery One in Denver, our neurosurgeons remove a tiny piece of the occipital bone, which is located in the lower back portion of the skull. This is known as a craniectomy, which is removing part of the skull to relieve pressure. After the portion of the skull is removed, the dura — the outer membrane of the spinal cord and brain — is cut and made larger to allow for more space for the brain.